This invention relates generally to a signal processing device preferably being used when digital broadcasting programs broadcast through an arbitrary network are transmitted to another network, and a switching method of signal processors suitable for use in the signal processing device. More specifically, this invention relates to a signal processing device being able to transmit the digital broadcasting programs broadcast through a first network to a second network by detecting a NIT (Network Information Table) from digital broadcast data on the first network, changing the NIT so as to be applicable to the second network and substituting said changed NIT for the NIT of digital broadcast data on the first network to obtain digital broadcast data on the second network.
Further, this invention relates to a signal processing device wherein when an used signal processor fails, a spare (redundant) signal processor is set as a used signal processor and the faulty used signal processor is set as a spare signal processor, thereby making it possible to simplify its configuration and to provide its simple management.
It is considered that the digital broadcast programs broadcast through an arbitrary network are transmitted to another network such as, the case in which a cable television enterprise or the like provides delivery service of a satellite digital multi-channel broadcast with transmitting device for modulation and conversion or the like by using its own network. In this case, however, it is impossible to transmit the digital broadcast programs broadcast through the first network to the second network only by changing modulation method with the transmitting device for modulation and conversion or the like, because the digital broadcast data includes the NIT having a physical information on a transmission path.
Accordingly, it is an object of the invention to provide a signal processing device wherein the digital broadcasting programs broadcast through a first network is transmitted to a second network by substituting the NIT suitable for the second network for the NIT of digital broadcast data on the first network.
Another object of this invention is to provide a signal processing device being capable of detecting whether said NIT is substituted correctly.
A further object of this invention is to provide a signal processing device including a spare signal processor making it possible to simplify its configuration and to provide its simple management.
According to a first aspect of the invention, we provide a signal processing device for converting a first digital broadcast signal having a predetermined transmission frequency on a first network signal into a second digital broadcast signal having a predetermined transmission frequency on a second network comprising demodulating means for demodulating said first digital modulated signal to obtain digital broadcast data, a first table-detecting means for detecting a NIT having a physical information relating to a transmission path from said digital broadcast data obtained by said demodulating means, table-changing means for changing said NIT detected by said first table-detecting means so that the table may be applicable to said second network, table substitution means for substituting the NIT changed by said table-changing means for the NIT of said digital broadcast signal obtained by said demodulating means, modulating means for modulating said digital broadcast data the NIT of which said table substitution means has substituted, to obtain a second digital modulated signal, and a first frequency-converting means for frequency-converting said second digital modulated signal to obtain a second digital broadcast signal.
The first digital broadcast signal on the first network has a predetermined transmission frequency. A frequency of said first digital broadcast signal is frequency-converted by a second frequency-converting means so that the digital modulated signal may be obtained. Then, the digital broadcast data on the first network are obtained by demodulating said digital modulated signal. Such digital broadcast data on the first network have the NIT being applicable to the first network.
The first table-detecting means detects the NIT from digital broadcast data on the first network and the table-changing means changes said NIT so that the NIT is applicable to said second network. For example, when a cable television enterprise or the like provides delivery service of a satellite digital multi-channel broadcast with transmitting device for modulation and conversion or the like by using its own network, a frequency information of the NIT is changed. Further, preferably, said table-changing means deletes an information relating to the digital broadcast signal failing to correspond to a digital information signal on said second network, from the digital broadcast signal on said first network when the number of digital broadcast signal on said second network becomes less than the one of digital broadcast signal on said first network.
The table substitution means substitutes said NIT changed so as to be applicable to the second network for the NIT of the digital broadcast data on the first network and forms the digital broadcast data on the second network. The modulating means modulates said digital broadcast data on the second network to obtain the digital modulated signal, and the first frequency-converting means frequency-converts said digital modulated signal to obtain a second digital broadcast signal to be broadcast on the second network. Thereby, a digital broadcast program broadcast through the first network may be transmitted to the second network.
Additionally, the signal processing device of this invention may be provided with a second table-detecting means for detecting a NIT from the digital broadcast data the NIT of which said table substitution means has substituted, and a substitution detecting means for comparing the NIT detected by said second table-detecting means and the NIT changed by said table-changing means and detecting whether said table substitution means substitutes the NIT correctly. When said substitution of NIT is carried out correctly, the NIT detected by the second table-detecting means is coincided with the one changed by the table-changing means.
A user may detect whether or not the substitution of NIT is carried out correctly by representing the detected result of the substitution with, for example, a display. Preferably, the signal processing device of this invention may be provided with a control means for controlling the first table-detecting means and the table substitution means so that said first table-detecting means detects the table again from the digital broadcast data modulated by said modulating means when said table substitution means detects that said substitution is carried out incorrectly, and said table substitution mean substitute the table changed by the table-changing means for the table detected again by the table-detecting means.
According to another aspect of the invention, we provide a signal processing device comprising a plurality of signal processors including at least one spare signal processor, wherein an used signal processor of said signal processors, excluding said spare signal processor, processes signals on a parallel basis, and switching control means for, when said used signal processor processing a signal fails, controlling said spare signal processors so that the one of said spare signal processors is switched to said used signal processor for processing said signal. Further, a signal processing device may be so constructed that the failed one of the signal processors is switched to the spare signal processor.
Further, according to the still another aspect of the present invention we provide a switching method of signal processors suitable for use in a signal processing device which has a plurality of signal processors respectively including tuner means and a circuit for processing signals outputted from said tuner means and allows an used signal processor, excluding a spare signal processor, of said plurality of signal processors to process broadcast signals having a transmission frequency, comprising the following steps of switching one of said spare signal processors to the signal processor for processing the broadcast signal having said one transmission frequency when said used signal processor processing a broadcast signal having one transmission frequency fails, switching said faulty one of the used signal processors to a spare signal processor, allowing a received frequency of said tuner means of said spare signal processor to coincide with a received frequency of said tuner means of said used signal processor, and allowing a processed state of said processing circuit included in said spare signal processor to coincide with a processed state of said processing circuit included in said used signal processor, and thereafter switching said spare signal processor to the used signal processor for processing the broadcast signal having said transmission frequency.
In the present invention, there is a plurality of signal processors. Of the plurality of signal processors, one or a plurality of used signal processors excluding one or a plurality of spare signal processors process one or a plurality of signals in parallel basis. When P signal processors are provided, for example, Q signal processors are set as used signal processors so as to perform signal processes on a parallel basis, whereas other (P-Q) signal processors are respectively placed in a standby state as spare signal processors.
When the one of the used signal processors fails in this state, one spare signal processor is switched to a used signal processor for processing a signal, and a faulty one signal processor is switched to a spare signal processor. Thus, the unfixed configuration of the spare (redundant) signal processor makes it unnecessary to provide changeover switches for performing switching between the used signal processors and the spare signal processor. For example, switch units for determining whether respective output signals of a plurality of signal processors should be respectively outputted, may simply be provided on the output sides of the plurality of signal processors, whereby their configuration can be simplified.
Further, since the spare (redundant) signal processors are so constructed as to be unfixed, the need for placing a faulty signal processor from the spare signal processor back onto the used signal processor is eliminated even if a failure of the faulty signal processor is removed, whereby its management becomes simple.
Preferably, in this invention, when a plurality of signal processors respectively have tuner means and circuits for processing output signals of the tuner means, and one spare signal processor is set as the used signal processor for processing a signal, for example, a received frequency or the like of the tuner means of one spare signal processor may be made coincident with that of the tuner means of faulty used signal processor. Thereafter, a switch unit provided so as to correspond to one spare signal processor may be brought into conduction. Thus, only an output signal similar to that obtained in the faulty used signal processor can be obtained from the switch unit. When the switch unit is composed of a variable attenuator, it is possible to prevent a noise from generating in switching the unit from conduction state to cutoff state and from cutoff state to conduction state.